A Survey of Music Theory for the College Classroom: Fundamentals

Triads and Seventh Chords

Chords

Chords are combinations of three or more pitch classes that are sounded together simultaneously or in an arpeggio. The chord types that we will learn about in this chapter are built of stacked major and minor thirds and are called triads and seventh chords. The four types of triads and the five most common seventh chords are extremely important in Western music. Each has a different structure and a unique sound. The structures of these chords should be memorized.

The charts below illustrate the seven possible spellings for triads and seventh chords using the natural notes of the musical alphabet. Accidentals (♯, ♭, ♮, x, ♭♭)  can be added to these notes as needed. The root is the note upon which a triad or seventh chord is built.

Triads
R 3rd 5th
C E G
D F A
E G B
F A C
G B D
A C E
B D F

Seventh chords
R 3rd 5th 7th
C E G B
D F A C
E G B D
F A C E
G B D F
A C E G
B D F A

The Four Triads

The four types of triads are illustrated below. The bottom note in each case is the root of the chord.

  • The major triad consists of a M3 and P5 above the root. This chord can also be understood as stacked thirds with a M3 above the root and a m3 above the third.
  • The minor triad consists of a m3 and P5 above the root. This chord can also be understood as stacked thirds with a m3 above the root and a M3 above the third.
  • The diminished triad consists of a m3 and o5 above the root. This chord can also be understood as stacked thirds with a m3 above the root and a m3 above the third.
  • The augmented triad consists of a M3 and +5 above the root. This chord can also be understood as stacked thirds with a M3 above the root and a M3 above the third.

four types of triads

The Five Seventh Chords

The five types of seventh chords are illustrated below. The bottom note in each case is the root of the chord.

  • The major seventh chord consists of a M3, P5, and M7 above the root. It can be viewed as a major triad with a major seventh or understood as stacked thirds with a M3 above the root, a m3 above the third, and a M3 above the fifth.
  • The dominant seventh or major-minor seventh chord consists of a M3, P5, and m7 above the root. It can be viewed as a major triad with a minor seventh or understood as stacked thirds with a M3 above the root, a m3 above the third, and a m3 above the fifth.
  • The minor seventh chord consists of a m3, P5, and m7 above the root. It can be viewed as a minor triad with a minor seventh or understood as stacked thirds with a m3 above the root, a M3 above the third, and a m3 above the fifth.
  • The half-diminished seventh chord consists of a m3, o5, and m7 above the root. It can be viewed as a diminished triad with a minor seventh or understood as stacked thirds with a m3 above the root, a m3 above the third, and a M3 above the fifth.
  • The diminished seventh chord (sometimes called the fully diminished seventh chord) consists of a m3, o5, and o7 above the root. It can be viewed as a diminished triad with a diminished seventh or can be understood as stacked thirds with a m3 above the root, a m3 above the third, and a m3 above the fifth.

five types of seventh chords

Circle of Thirds

These chord spellings can be illustrated on the “circle of thirds,” which is a visual aid for identifying and building triads and seventh chords. The pitch classes of a triad or seventh chord are always next to one another on this circle. This graphic should be read clockwise. For example, the pitches A – C – E form a triad. The pitches B – D – F – A form a seventh chord.

circle of thirds

Writing Triads and Seventh Chords

After the structures of these various chords are memorized, writing them becomes easy. Use your interval writing skills to your advantage. It is especially helpful to have all the white key thirds memorized.

Example: Write a minor chord on the following root.

writing a triad

Step #1 Fill in the needed notes above the given note. The root of this chord is E, so the chord will be spelled using the notes G and B.

Step #2 What type of third is G above E? It is a M3, so it must be lowered by one half step (semitone) to become a m3.

Step #3 You can either write a M3 above the G or you can write a P5 above the E.

Example: Write a Mm7 chord using the given note as the fifth of the chord.

writing a seventh chord

Step #1 Fill in the root, third, and seventh.               

Step #2 Because the B (the fifth of the chord) is given, it cannot be changed. The top interval of a Mm7 chord is a m3. Find the m3 above B.

Step #3 Find the m3 below B.

Step #4 You can either find the M3 below the G or a P5 below the B. Either will yield the correct answer.

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